U.S. patent number 6,158,729 [Application Number 09/208,800] was granted by the patent office on 2000-12-12 for compact, stiff, remotely-actuable quick-release clamp.
This patent grant is currently assigned to The United States of America as represented by the Administrator of the National Aeronautics and Space Administration. Invention is credited to Ted W. Tsai.
United States Patent |
6,158,729 |
Tsai |
December 12, 2000 |
Compact, stiff, remotely-actuable quick-release clamp
Abstract
The present invention provides a clamp that is compact and
lightweight, yet provides high holding strength and stiffness or
rigidity. The clamp uses a unique double slant interface design
which provides mechanical advantages to resist forces applied to
the clamp members as the load increases. The clamp allows for rapid
and remote-activated release of the clamp jaws by applying only a
small operating force to an over-center lock/release mechanism,
such as by pulling a manual tether.
Inventors: |
Tsai; Ted W. (Houston, TX) |
Assignee: |
The United States of America as
represented by the Administrator of the National Aeronautics and
Space Administration (Washington, DC)
|
Family
ID: |
22776119 |
Appl.
No.: |
09/208,800 |
Filed: |
November 24, 1998 |
Current U.S.
Class: |
269/228; 269/136;
269/201 |
Current CPC
Class: |
B25B
5/12 (20130101); B25B 5/16 (20130101) |
Current International
Class: |
B25B
5/16 (20060101); B25B 5/12 (20060101); B25B
5/00 (20060101); B25B 005/12 () |
Field of
Search: |
;269/228,201,136,238,239
;254/15-17 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Scherbel; David A.
Assistant Examiner: Wilson; Lee
Attorney, Agent or Firm: Cate; James M.
Claims
What is claimed is:
1. A clamp comprising: a first jaw having a workpiece contacting
end, a central fulcrum, and a cantilever element;
a second jaw having a workpiece contacting end and a central
fulcrum coupled to the central fulcrum of the first jaw;
a third member pivotally coupled to the second jaw, the third
member being disposed to contact the cantilever element of the
first jaw; and
a hook disposed between the third member and the cantilever element
to retain the cantilever in contact with the third member.
2. The clamp of claim 1, further comprising an over-center
mechanism engaging the fourth member.
3. The clamp of claim 1, further comprising a slide link assembly
disposed between the third member and the first jaw.
4. The clamp of claim 1, further comprising a spindle bolt
extendible from one of the jaws to contact the workpiece.
5. The clamp of claim 1, wherein the third member has a wedge
portion disposed to contact the cantilever element of the first
jaw.
6. The clamp of claim 1, wherein the fourth member is a hook.
7. The clamp of claim 6, further comprising a lock member for
releasably securing the hook in contact with the cantilever
element.
8. The clamp of claim 1, wherein a portion of the third member is
rigidly disposed between the first and second jaws.
9. A clamp, comprising:
a first jaw having a workpiece contacting end, a central fulcrum,
and a cantilever element having first and second opposed
surfaces;
a second jaw having a workpiece contacting end and a central
fulcrum coupled to the central fulcrum of the first jaw;
a third member pivotally coupled to the second jaw about a first
axis, the third member is disposed to contact the first opposed
surface of the cantilever element along a first interface, wherein
the first interface forms an outwardly opening angle with a line
tangent to the first axis; and
a fourth member pivotally coupled to the third member about a
second axis, the fourth member disposed to contact the second
opposed surface of the cantilever element along a second interface,
wherein the second interface forms an outwardly opening angle with
a line tangent to the second axis.
10. The clamp of claim 9, wherein a load applied between the first
and second jaws transmits a first kick load to the third
member.
11. The clamp of claim 10, wherein the first kick load transmits a
smaller, second kick load to the fourth member, and further
comprising a locking member to releasably oppose the second kick
load.
12. The clamp of claim 9, wherein the third member has a wedge
portion disposed to contact the first opposed surface, wherein the
fourth member has a wedge portion disposed to contact the second
opposed surface, and further comprising a locking member to
releasably secure the wedge portion of the fourth member in contact
with the second opposed surface.
13. The clamp of claim 12, wherein the locking member comprises an
over-center mechanism.
14. The clamp of claim 9, further comprising a slide link assembly
disposed between the third member and the first jaw.
15. The clamp of claim 9, further comprising a spindle bolt
disposed through a jaw to contact the workpiece.
16. A clamp, comprising:
a first jaw having a workpiece contacting end, a central fulcrum,
and a cantilever element having a load transmitting surface;
a second jaw having a workpiece contacting end and a central
fulcrum coupled to the central fulcrum of the first jaw;
a load bearing member pivotally coupled to the second jaw, the load
bearing member displaceably disposed to contact the load
transmitting surface of the cantilever element; and
a hook pivotally coupled to the load bearing member, the hook
displaceably disposed to secure the load bearing member in contact
with the load transmitting surface.
17. The clamp of claim 16, further comprising a lock pivotally
coupled to the load bearing member.
18. The clamp of claim 17, wherein the lock comprises an
over-center mechanism.
19. The clamp of claim 18, wherein the over-center mechanism
engages an arm of the load bearing member.
20. The clamp of claim 19, wherein the over-center mechanism
comprising a roller which engages the arm.
21. The clamp of claim 20, the over-center mechanism having a
pivotal mounting permitting it to be pivoted beyond an over-center
position further comprising a set screw disposed to the arm for
adjusting the permitted pivotal movement of the over-center
mechanism beyond its over-center position.
22. An apparatus comprising:
(a) a plurality of clamping members, each clamping member
comprising:
(i) a first jaw having a clamping end, a central fulcrum, and a
cantilever element;
(ii) a second jaw having a clamping end and a central fulcrum
coupled to the central fulcrum of the first jaw element;
(iii) a third member pivotally coupled to the second jaw, the third
member disposed to contact the cantilever of the first jaw; and
(iv) a hook disposed between the third member and the cantilever
element to retain the cantilever element in contact with the third
member;
(b) a first workpiece contacting plate coupled to the clamping end
of the first jaw of each clamping member; and
(c) a second workpiece contacting plate coupled to the clamping end
of the second jaw of each clamping member, wherein the central
fulcrums of each clamping member have a common axis.
Description
ORIGIN OF THE INVENTION
The invention described herein was made by and employee of the
United States Government and may be manufactured and used by or for
the Government of the United States of America for governmental
purposes without the payment of any royalties thereon or
thereafter.
FIELD OF THE INVENTION
The present invention relates to a high strength clamp that can be
released by hand. More particularly, the present invention relates
to a high strength clamp with jaws that can be remotely released
and which open widely upon release.
BACKGROUND OF THE RELATED ART
High strength clamps are useful in various industrial applications,
typically holding two or more members in place during a procedure
of limited duration. For example, a high strength clamp may be used
to hold together two structural steel members while the members are
welded together. As another example, a high strength clamp may be
used to secure heavy equipment to a truck during transport of the
equipment from one location to another. As yet another example, a
high strength clamp may be used to connect two pipe flanges
together while another, more permanent type of fastener is
installed or removed, such as bolts, rivets or screws.
One particularly demanding application for high strength clamps is
the contingency demating procedure (separation) of aerospace
structures, e.g., of the Space Shuttle from either the Russian MIR
or the Space Station. This procedure requires a lightweight, high
strength and remotely releasable clamping tool for securing the
docking module halves of NASA's Orbiter Docking System (ODS) during
removal of ninety-six 1/4 inch bolts. The docking module halves
define a flanged, circumferential interface sealed by two O-rings,
highly loaded, therebetween. Typically, two high strength clamps
are placed about 180 degrees apart to hold the interfacing flanges
together while the bolts holding them are removed by astronauts.
The clamps must have sufficient holding strength and rigidity to
oppose the seal and external loads, which can exceed about
ten-thousand pounds, and thereby assure the integrity of even the
final few remaining bolts and prevent any premature or partial
separation of the interfacing flanges. After the removal of the
bolts, the astronauts can safely execute the separation by
releasing the two clamps, preferable by remote activation under an
operating force no greater than 25 pounds. It is also preferred
that the clamp jaws open at least 90 degrees upon release to clear
the working area and allow for an unobstructed separation of the
two flanges.
Cross-sectional side views of a prior art toggle action clamp 10,
otherwise known as the Orbiter Docking System 96-bolt contingency
clamp, are shown in FIGS. 1 and 2 in the open (released) position
and the closed (clamped) position, respectively. This clamp uses a
conventional over-center toggle action mechanism 12 with an
actuating lever 14 for clamping (FIG. 2) and releasing (FIG. 1) the
interfacing flanges 16,18. In order to achieve a low operating
force, the clamp gains leverage by incorporating the handle 14
having a substantial assembled length of 32 inches. To further
lower the operating force required to release the clamp, the
over-center toggle is limited to angles less than one degree
(<1). The long linkages 20 of this and other toggle-type clamps
are inherently less stiff than other clamp designs and do not
maximize the stiffness-to-weight ratio. In fact, this clamp design
must be enhanced to achieve the high stiffness and strength
necessary for this application, and results in each clamp weighing
a substantial 22 pounds.
Another disadvantage of the prior art toggle action clamp is its
sensitivity to friction occurring within the joints or pivots 22 of
the toggle mechanism. As the axial load in the linkages 20
increases, the frictional forces within the joints 22 that oppose
rotation of the linkages increase proportionally, as does the
operating force required to release the clamp. Polishing the mating
surfaces of linkages decreases the amount of the friction in the
joints, but when the linkages are under loads of several thousand
pounds, the friction is still significant.
Despite attempts to facilitate release of the prior art clamp 10,
release of the clamp still requires an excessive force exceeding
the standard 25 pound allowable force for manned space operations.
Consequently, an additional winch tool (not shown) must be
connected to the end 24 of the long handle 14 in order to release
the clamp 10 under such a high load. Using a winch tool further
complicates the contingency extravehicular operation for demating
of the docking system (represented by flanges 16,18). The clamp
also requires certain undesirable maintenance procedures, including
calibration and pre-flight checkout.
Therefore, there is a need for a high-performance clamp that
provides a high holding force, yet requires only a minimal force to
release the clamp. It would be desirable if the clamp could be
released by hand, preferably with less than 25 pounds of force. It
would also be desirable if the clamp could open fully during
release to allow easy separation of the clamped objects. It would
be further desirable if the clamp were both lightweight and
compact. It will be understood by those in the art that such
characteristics are of importance and benefit in various
ground-based applications of such clamps, in addition to the
context of the illustrative aerospace example just described.
SUMMARY OF THE INVENTION
The present invention provides a clamp comprising a first jaw
having a workpiece contacting end, a central fulcrum and a
cantilever, as well as a second jaw having a workpiece contacting
end and a central fulcrum coupled to the central fulcrum of the
first jaw. A third member is pivotally coupled to the second jaw so
that the third member is disposed to contact the cantilever of the
first jaw and maintain the spacing between the first and second
jaws. A fourth member, or hook, is disposed between the third
member and the cantilever to retain the cantilever in contact with
the third member. A locking member, such as an over-center
mechanism, may also be provided for releasably securing the hook in
contact with the cantilever.
It is preferred that the clamp apply at least a snug down load to a
workpiece using a spindle bolt disposed through a jaw to contact
the workpiece. It is also preferred that the clamp also comprise an
over-center mechanism to engage and retain the fourth member. An
optional slide link assembly may be disposed between the third
member and the first jaw to allow one hand operation of the
clamp.
In accordance with another aspect of the present invention, a
clamp, as described above, includes a cantilever having first and
second opposed surfaces, wherein the third member is disposed to
contact the first opposed surface of the cantilever and the fourth
member is disposed to contact the second opposed surface of the
cantilever. The slanted surfaces of the third and fourth members
may be formed by wedge portions disposed to contact the first and
second opposed surfaces, respectively. A locking member may then be
incorporated to releasably secure the wedge portion of the fourth
member in contact with the second opposed surface.
In yet another aspect of the present invention, the clamp comprises
a first jaw having a workpiece contacting end, a central fulcrum
and a cantilever having a load transmitting surface, as well as a
second jaw having a workpiece contacting end and a central fulcrum
coupled to the central fulcrum of the first jaw. A load bearing
member is pivotally coupled to the second jaw so that the load
bearing member is displaceably disposed to contact the load
transmitting surface of the cantilever. A hook, pivotally coupled
to the load bearing member, is displaceably disposed to secure the
load bearing member in contact with the load transmitting surface.
The hook is secured by a locking mechanism pivotally coupled to the
load bearing member. Where the locking mechanism is an over-center
mechanism, the mechanism comprises a roller which engages a cradle
formed in an arm of the load bearing member. A set screw is
preferably disposed through the arm for adjusting the over-center
angle.
The invention also provides an apparatus comprising a plurality of
clamping members. Each clamping member comprises a first jaw having
a clamping end, a central fulcrum, and a cantilever; a second jaw
having a clamping end and a central fulcrum coupled to the central
fulcrum of the first jaw; a third member pivotally coupled to the
second jaw, the third member disposed to contact the cantilever of
the first jaw; and a hook disposed between the third member and the
cantilever to retain the cantilever in contact with the third
member; a first workpiece contacting plate coupled to the clamping
end of the first jaw of each clamping member; and a second
workpiece contacting plate coupled to the clamping end of the
second jaw of each clamping member, wherein the central fulcrums of
each clamping member have a common axis.
BRIEF DESCRIPTION OF THE DRAWINGS
So that the above recited features and advantages of the present
invention can be understood in detail, a more particular
description of the invention, briefly summarized above, may best be
understood with reference to the embodiments which are illustrated
in the appended drawings. It is to be noted, however, that the
appended drawings illustrate only typical embodiments of this
invention and are therefor not to be considered limiting of its
scope, for the invention may admit to other equally effective
embodiments.
FIG. 1 is a cross-sectional side view of a prior art toggle action
clamp in the open position;
FIG. 2 is a cross-sectional side view of the prior art toggle
action clamp of FIG. 1 in the closed position to secure two flanged
members;
FIG. 3 is a front perspective view of a high strength clamp of the
present invention;
FIG. 4 is a back perspective view of the high strength clamp of
FIG. 3;
FIG. 5 is a side view of the high strength clamp of FIG. 3 in an
open position and including an optional slide link assembly;
FIG. 6 is a partial cross-sectional side view of the high strength
clamp of FIG. 5 in a partially closed position; and
FIG. 7 is a partial cross-sectional side view of the high strength
clamp of FIG. 6 in a fully closed position.
FIG. 8 is a top view of an apparatus incorporating two clamping
members having common workpiece contacting plates.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
The present invention generally provides a clamp that is compact
and lightweight, yet provides high holding strength and stiffness
or rigidity. The clamp uses a unique double slant interface design
which provides mechanical advantages to resist forces applied to
the clamp members as the load increases. The clamp allows for rapid
and remote-activated release of the clamp jaws by applying only a
small operating force to an over-center lock/release mechanism,
such as by pulling a manual tether.
The clamp incorporates first and second jaws having fulcrums that
are pivotally coupled together. Adjacent ends of the two jaws are
configured as workpiece contacting ends. A first jaw has a
cantilever end extending generally opposite the workpiece
contacting end and beyond the fulcrum. The second jaw has a third
member pivotally coupled to the second jaw, preferably at a point
adjacent the cantilever of the first jaw. The third member is a
load bearing member that acts as a spacer or wedge to secure the
first and second jaws in a rigid, fixed relationship by resisting
compressive forces transmitted through the jaws from the
workpiece.
A fourth member, such as a hook, is releasably disposed to retain
the cantilever in contact with the third member. It is preferred to
have the fourth member pivotally coupled to either the cantilever
or the third member, most preferably the third member, in order to
avoid having loose parts and to simplify the application of the
clamp to a workpiece. The fourth member can be disposed to prevent
the third member from being displaced from a position between the
cantilever and the second jaw. In this closed or hooked position,
the fourth member prevents the clamp from opening.
Once the clamp is assembled in place around a workpiece, a
snug-down load is applied to the workpiece by the workpiece
contacting ends of the jaws. It is preferable that at least one of
the jaws include a threaded spindle bolt extending therethrough to
form an adjustable workpiece contacting surface. It may also be
preferred, according to specific applications, that the workpiece
contacting end have workpiece contacting surfaces contoured to mate
with, or otherwise accommodate, features of the workpiece. For
example, a clamp being used to secure two flanges may include a jaw
with a slot or cutout for placement over bolt heads or nuts.
Once the clamp applies a snug-down load, the clamp remains rigid
and provides a high holding strength to the clamped workpiece(s)
during the performance of some procedure on the workpiece, such as
fastening or unfastening two workpieces. For example, the jaws may
be used to clamp two flanges having O-rings or other gasketing
material therebetween which produce a force against each workpiece
contacting end of the jaws. Because the jaws are pivotally coupled
at their fulcrums, these forces are transmitted as a rotational
force through each jaw. The third member is positionable between
the cantilever of the first jaw and the second jaw to resist or
oppose these rotational forces. Once the procedure being performed
on the workpiece is complete, the clamp is released by disengaging
the fourth member, removing the third member from contact with the
cantilever, and separating the workpiece contacting ends.
In one aspect of the invention, the cantilever of the first jaw has
a first surface for contacting the third member and a second
surface, opposed from the first surface, for contacting or
receiving the fourth member. When the clamp is closed and a load is
applied, the first surface and the third member are in facing
contact under a compressive load. It is preferred that the contact
between the first surface of the cantilever and the third member
define an interface that is slanted relative to the rotational
direction of the load. The slant is provided at such an angle that
the load at the interface produces a compressive load and a kick
load on the third member, wherein the kick load is a minor portion
of the load on the third member. The compressive load is
transmitted directly to the second jaw and the kick load is
directed to swing the third member away from, and out of contact
with, the cantilever. However, it may also be desirable to provide
a slight interference fit between the third member and the second
jaw to limit the extent of the swing.
The function of the fourth member is to resist or oppose the kick
load and retain the third member in contact with the cantilever. It
is preferred that the contact between the second surface of the
cantilever and the fourth member define a second interface that is
slanted relative to the direction of the kick load applied to the
third member. This slanted interface is provided at such an angle
that the load at the second interface, which is proportional to the
kick load on the third member, produces a tensile load and a kick
load on the fourth member, wherein the kick load is a minor portion
of the load on the fourth member. The tensile load is transmitted
directly to the second surface of the cantilever and the kick load
is directed to swing the fourth member away from, and out of
contact with, the cantilever.
The slope of the slanted interfaces is dependent on the finish of
the contacting or load bearing surfaces. The clamp is preferably
made of a high strength steel material, although it can be made of
aluminum or other rigid materials known in the art depending on the
magnitude of the load of application. It is generally preferred
that both surfaces of each slanted interface be polished and coated
(e.g., with solid film lubrication/Teflon coating/epoxy glass) to
within a desired range of boundary friction. Once a surface finish
or coating has been chosen and the corresponding ranges of friction
determined, the slope or angle of the slanted interfaces that will
produce a desired kick load can be easily determined and verified
by simple tests.
Where the clamp of the present invention incorporates the two
slanted interfaces described above, it is preferred that the clamp
also incorporate a lock/release mechanism for resisting or opposing
the kick load on the fourth member and releasably secure the fourth
member in a closed position. The clamp is released by operating the
lock/release mechanism, preferably by pulling a manual tether or
cord connected to the lock/release mechanism. The amount of force
required to release the clamp may be tailored to a specific
application, as will be described below, and is preferably low
enough for manual operation, most preferably below about 25 pounds
of force.
In another aspect of the invention, the lock/release mechanism
comprises an overcenter mechanism disposed between the fourth
member and an arm extending from some other member of the clamp,
preferably the third member. A preferred over-center mechanism is
pivotally coupled at one end and includes a roller on the other
end. The roller is received in a cradle by applying a locking force
which pushes the roller past into a stable position just
"over-center," i.e. just past the point of greatest resistance. It
is preferred that the cradle include an adjustment device, such as
a set screw, for limiting how many degrees over-center the roller
is allowed to pass. Whereas any over-center angle greater than zero
degrees may be used, it is preferred to limit the degrees
over-center. Limiting the degrees over-center reduces the operating
force necessary to release the over-center mechanism. It is further
preferred that the cradle and set screw allow adjustment between
about 1 and about 5 degrees over-center so that the operating force
is less than the kick load on the fourth member. It is also
preferred that the over-center mechanism be pivotally coupled to
either the fourth member or an arm extending from the third member
and engage a cradle formed in an opposed surface of either the
third or fourth members, respectively.
Upon release of the lock/release mechanism, the kick loads cause
the fourth and third members to automatically swing away from their
engaged positions, thereby releasing the forces applied to the
workpiece and allowing the jaws of the clamp to fully open. In
fact, it is most preferred that the kick loads cause the fourth and
third members to swing away with sufficient force that the jaws of
the clamp are automatically pulled to a fully open position. An
automatic and forced opening of the clamp facilitates remote
releasing and withdrawal of the clamp. Furthermore, a fully open
position, such as about 90 degrees, is necessary in some
applications of the clamp, such as the docking of two space crafts,
to allow an unobstructed separation of the workpieces.
In another aspect of the invention, the clamp is provided with an
optional slide link assembly. The assembly is generally disposed
between the third member and the first jaw so that the first jaw
does not independently rotate about the fulcrum, thereby
complicating the positioning of the clamp onto a workpiece.
Furthermore, the assembly is designed so that the act of pivoting
the third member towards the cantilever causes the first jaw to
close onto the workpiece prior to the third member actually making
contact with the cantilever. The slide link provides the benefit of
positioning and closing the clamp onto a workpiece with a single
hand.
The clamp of the present invention can be made very small and
lightweight, yet rigid and strong. While a lightweight clamp is
generally desirable in most applications, weight is a major
consideration in space flight, particularly at higher orbital
inclinations such as that used for the international space station.
A preferred clamp of the present invention can be made weighing
only 10 pounds, yet hold a load greater than 10,000 pounds. It
should be recognized, however, that the clamp may be made having
various sizes, weights and holding capacities depending upon the
particular application. For example, it is believed that the clamp
would be particularly beneficial in securing pipe or vessel flanges
during welding, assembly or disassembly; truck or boat docking
equipment; heavy machine work and assembly; temporary structures,
barricades and bulkheads; and the like.
It may also be desirable to incorporate a plurality of clamping
members along the length of a pair of common workpiece contacting
plates. Each clamping member would operate independently except
that the first and second jaws of each clamping member must move
simultaneously. In this manner, the strength and rigidity of a
plurality of clamping members may be provided over an enlarged
area. In order for the jaws to open and closed smoothly or at all,
the central fulcrums of each clamping member should have a common
axis.
Now referring to FIGS. 3 and 4, front and back perspective views of
a high strength clamp 30 of the present invention are shown. The
clamp 30 has a first member, hereinafter referred to as the first
jaw 32, with a spindle bolt 34 extending therethrough to form a
workpiece contacting surface 36, a fulcrum defined by a pin hole
and pivot pin with flanged bushing 38, and a cantilever 40
extending generally opposite of the workpiece contacting end of the
first jaw 32. A second member, hereinafter referred to as the
second jaw 42, includes a workpiece contacting surface 44 with
tailored cutouts 46 formed therein, a fulcrum defined by a pair of
parallel lugs 48 receiving the fulcrum of the first jaw 32, and a
pair of parallel lugs 50 with pivot pin and flanged bushings 52 for
pivotally coupling with a third member or load rod 54.
The third member 54 includes a fourth member or hook 56 that is
pivotally coupled thereto about a pivot pin with flanged bushings
58. The fourth member 56 engages the cantilever 40 to prevent the
third member 54 from swinging away from the cantilever 40 (out of
the page in FIG. 4). In turn, an over-center lock/release mechanism
60 is pivotally coupled to the fourth member 56 at the opposite end
of the fourth member from the pivot. The lock/release mechanism 60
has a roller 62 (better shown in FIG. 5) which engages a cradle 64
formed in the arm portion 66 of the third member 54. The clamp 30
can be remotely released by applying an operating force to a tether
line 68 coupled to the link 70 of the lock/release mechanism
60.
Now referring to FIGS. 5-7, partial cross-sectional side views of
the high strength clamp 30 of FIG. 3 are shown in an open position,
a partially closed position and a fully closed position,
respectively, and including an optional slide link assembly 72.
Referring specifically to FIG. 5, the clamp 30 is initially
positioned for clamping the two flanges 16,18 by placing the
workpiece handling surface 44 of the second jaw 42 on one side of
the mating flanges. The cutout 46 receives the extruded nutplate or
gusset 19 to allow the surface 44 to make direct and full contact
with the flange 18.
The first jaw 32 and the third member 54 are both pivotally
connected to and disposed relative to the second jaw 42 about
substantially parallel axis defined by the pivot pin with bushings
38, and the pivot pin with bushings 52, respectively. The first jaw
32 and the third member 54 are additionally mutually coupled by an
optional slide link assembly 72. The assembly 72 comprises a slide
link 74 with a first end pivotally coupled to the third member 54
at a fixed pivot point 76. The second end 78 of the slide link 74
includes a guide pin track 80 that slidably engages a guide pin 82
which extends from one side of the first jaw 32. As the third
member 54 is rotated towards the first jaw 32 (clockwise as shown
in FIGS. 5-7), the slide link end 78 pushes against a guide member
84 extending from the side of the first jaw 32. The force placed on
the guide member 84 is transmitted to the first jaw 32 and causes
the jaw 32 to rotate towards the workpiece 16,18 (clockwise as
shown in FIGS. 5-7).
Now referring primarily to FIG. 6, a partial cross-sectional side
view of the high strength clamp 30 of FIG. 5 is shown in a
partially closed position. Note that the slide link assembly is
designed to cause sufficient rotation of the first jaw 32 to allow
the slanted surface 86 of the third member 54 to make initial
contact with the cantilever 40 at point 88. The slide link 74 is
then allowed to pass around the guide member 84 causing no further
rotation of the first jaw 32. It is the direct contact between the
third member 54 and the first surface 90 of the cantilever 40 that
causes the first jaw 32 to complete its rotation.
Now referring to FIG. 7, a partial cross-sectional side view of the
high strength clamp 30 of FIG. 6 is shown in a fully closed
position. It is preferred that the full rotation of the first jaw
32 be limited by a stop member 92 extending from the lug 48 of the
second jaw 42. In this manner, rotation of the jaw 32 is completed
when the guide member 84 of the first jaw 32 engages the stop
member 92. It is also preferred that the guide member 84 and stop
member 92 make contact prior to, or simultaneous with, the spindle
bolt 34 making contact with the workpiece 16,18 so that the clamp
30 can be closed before applying a snug-down load. If desired, a
higher and pre-determined torque load can be applied to the spindle
bolt to produce a higher initial compressive pre-load on the
workpiece.
With the clamp 30 in the closed position, the slanted surface or
wedge portion 86 of the third member 54 is disposed in full contact
with the first surface 90 of the cantilever 40. The fourth member
or hook 56 is subsequently pivoted about pivot pin 58 until a
slanted surface 94 of the fourth member 56 is disposed in contact
with a second surface 96 of the cantilever 40.
Once the fourth member 56 is in full contact with the cantilever
40, the lock/release mechanism 60 can be rotated about pivot 98
(clockwise in FIGS. 5-7) with the force of a single finger until
the roller 62 is received within the cradle 64 and travels at least
one degree over-center. The exact number of degrees over-center
that the mechanism 60 will travel is adjustable by turning a
self-locking set screw 100 in threaded engagement through a portion
of the arm 66. With the lock/release mechanism 60 in the locked
position, the first and second jaws 32,42 are held in a rigid
relationship. If desired, a safety pin can be easily incorporated
for added security. The spindle bolt 34, with its threaded
engagement through the first jaw 32, is then turned to apply a load
on the workpiece 16,18.
In accordance with the present clamp design, as just described, the
clamp 30 remains in this position, under very high loads, until the
tether 68 is pulled by an operating force great enough to pull the
roller 62 out of the cradle 64. However, even when the clamp 30 is
under a load of about 10,000 pounds, the necessary operating force
is only about 25 pounds. Note that upon release of the lock/release
mechanism 60, the clamp 30 opens automatically in accordance with
FIGS. 5-7 viewed sequentially in reverse.
Now referring to FIG. 8, two clamping members 30 are connected to
and mutually spaced along the length of first and second curved
workpiece contacting plates 112. The plates 112 may be designed in
various shapes and sizes in accordance with a particular
application, such as a flange having a particular diameter. A
first, top plate 112 is coupled to the first jaw 32 of each
clamping member, and a second, lower plate 112 (not shown) is
coupled to the second jaw 42 (FIGS. 5-7). Other than the attachment
of the plates 112, the clamping members 30 operate in an identical
manner as the clamp of FIGS. 3-7. It should be noted that both
clamping members 30 must be released before the jaws and plates may
be opened. Additionally, since the clamping members 30 are rigidly
coupled by the common plates, it is necessary for the central
fulcrums of each clamping member to have a common axis so that the
apparatus can open.
The clamps of the present invention incorporate multiple slanted
interfaces making it possible to channel a relatively small and
pre-determined portion of a high clamp load into the release
mechanism. The slanted interfaces allow the channeled load to be
exponentially reduced, while maintaining a sufficiently steep slant
angle to assure a positive kick load that will open the clamp on
command. Unlike the previously discussed prior art toggle action
clamp, in which the joint friction always resists the handle
operation force, the present clamp is far less sensitive to the
joint friction. The joint friction in the main load path of the
clamp actually helps to reduce the release load. At release, the
slanted interfaces allow a complete and quick severance of the load
paths. Therefore, the components of the clamp can be as short and
compact as possible resulting in a truly optimized design with
minimum weight and maximized stiffness. The over-center
lock/release mechanism of the clamp allows the clamp to be unlocked
while still under a full load. The lock/release mechanism
preferably includes a roller which assures that the release
mechanism is less sensitive to the friction. The set screw allows
the over-center angle to be adjustable so that the corresponding
release load can be fine-tuned.
This invention is particularly useful for the assembly and
disassembly of various highly loaded gasketed joints. It is also
useful as a high-capability, quick-and-remote-release clamp for a
variety of applications, especially in hazardous environments like
outer space, pipeline repair and construction, fire fighting or
demolition. The invention may also be found useful in more common
applications, such as quick release C-clamps, jigs or fixtures.
Furthermore, the invention is useful in any application where it is
desired to have improved mechanical advantages, higher load
carrying capability and less volume and weight.
As an example, a clamp may be prepared in accordance with FIGS. 3-7
for application in NASA's Orbiter Docking System (ODS), having a
96-bolt interface contingency demating apparatus operable to
releasably connect the Space Shuttle to the Russian MIR, or the
International Space Station. The clamp preferably is tested along
side a prior art clamp, constructed in accordance with FIGS.
1-2.
The maximum length of the assembled clamp, including the handle
mount, may be only twelve inches, i.e., far shorter and lighter
than the 32-inch handle necessary to actuate the prior art clamp.
The main body of the clamp was less than 6 inches in width and was
capable of carrying an ultimate load greater than 30,000 pounds.
The clamp was found to be strong, stiff and lightweight. The total
weight of the clamp was less than 10 pounds, compared with the
22-pound prior art clamp. Because two clamps are required for the
contingency demating procedure, the present clamps provide a total
weight saving of 24 pounds for each Orbiter flight. The clamp also
required less space for storage and operation.
The operating force of the present clamp was measured at less than
25 pounds with a 10,000 pound load in the clamp. The prior art
clamp required a 35 pound operating force with only 5,700 pound
load in the clamp. When the load on the prior art clamp approached
10,000 pounds, a winch tool and additional procedures were required
for the release. The present clamp required none of these
additional procedure and no pre-flight calibration or
maintenance.
The operating force of the prior art clamp using a conventional
toggle action mechanism was adjustable only to a degree because it
was sensitive to the joint friction. The operating force of the
present clamp was easily adjusted to a desirable low level, making
it truly remotely releasable and user friendly. When high loads
were applied to the prior art clamp, a major portion of the
operating force was devoted just to overcome the joint friction. By
contrast, the clamp of the present invention was far less sensitive
to the joint friction under the same or greater loads.
While the foregoing is directed to a preferred embodiment of the
present invention, other and further embodiments of the invention
may be devised without departing from the basic scope thereof. The
scope of the invention is determined by the claims which
follow.
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